The present invention relates to an adjustable joint unit including a generally plate-shaped arm having a socket portion to which a closing member is attached so that a ball head portion of a ball joint can slidably be contained in the socket portion. The invention also relates to a method of producing such an adjustable joint unit.
Conventionally known examples of adjustable joint units provided with a generally plate-shaped arm having a socket portion to which a closing member is attached so that a ball head portion of a ball joint can slidably be contained in the socket portion is disclosed in Japanese Patent Public Disclosure No. 1998-100628.
The adjustable joint unit disclosed in Japanese Patent Public Disclosure No. 1998-100628 calls for pressing a steel plate so as to form a socket portion protruding from one of the two planar surfaces and a tubular portion on the other planar surface of the plate. The socket portion is formed in a generally cylindrical shape, and the vicinity of its outer end gradually or otherwise narrows towards the outer end, at which an aperture is opened. The tubular portion extends integrally and approximately coaxially with the socket portion. A bearing seat containing the ball head portion of a ball stud is housed in the socket portion, with the stud portion of the ball stud projecting from the aforementioned narrowing opening. A closing plate is fitted in the tubular portion""s opening, which is located at the end opposite the narrowing opening of the socket portion, and rotatable rollers are rolled so that the tubular portion is crimped in such a manner as to be inclined inward. Then, with a given preliminary load applied to the ball head portion, the closing plate is attached to cover the opening of the tubular portion.
However, the structure disclosed in Japanese Patent Public Disclosure No. 1998-100628 is incapable of improving the manufacturability of adjustable joint units, because it is necessary to form a tubular portion for crimping and securing the closing plate during the pressing process of the socket portion.
Examples of structures that call for containing a ball head portion in a socket by crimping include those disclosed in Japanese Patent Publication No.1977-29374 or Japanese Patent Public Disclosure No. 1993-76961.
Japanese Patent Publication No. 1977-29374 and Japanese Patent Public Disclosure No. 1993-76961 relate to a structure including a generally cylindrical socket portion open at both ends, in other words having an aperture portion located at one end and a mounting opening portion at the other end, wherein the aperture portion and the mounting opening portion respectively permit the ball head portion and the stud portion of a ball stud to be inserted therethrough; the ball head portion is inserted from the mounting opening portion into the socket portion and contained therein, with a bearing seat between the ball head portion and the socket portion; a closing plate is fitted in the mounting opening portion; rotatable rollers are rolled so that the end of the socket portion where the mounting opening portion is located is crimped in such a manner as to be inclined inward; and a given preliminary load applied to the ball head portion, thereby firmly attaching the closing plate to and covering the mounting plate portion.
However, conventional structures disclosed in Japanese Patent Publication No. 1977-29374 or Japanese Patent Public Disclosure No. 1993-76961 make it necessary to form the vicinity of the rim of the mounting opening portion thin enough to permit its shape to be changed by crimping so as to be inclined inward, thereby enabling the attachment of the closing plate. As it is necessary to specially provide the socket portion with a thin portion, the structure described above is unable to improve the manufacturability of adjustable joint units. Forming the end of the socket portion where the mounting opening portion is located thin makes it easy to be crimped inward. On the other hand, it presents the possibility of the crimped portion being deformed in such a manner as to flare outward should an external stress be applied to the ball stud. Such a deformation of the crimped portion may result in displacement of the closing plate, which may cause the ball stud to slip off of the socket portion. Furthermore, as the degree of reshaping performed by crimping the vicinity of the mounting opening portion inward is limited by various factors, such as the strength of the material and the thickness of the portion to be crimped, the area where it is in contact with the closing plate, too, is reduced. Should the mounting strength of the closing plate be reduced to such an extent as to allow a gap to be formed between the closing plate and the crimped portion, it may result in undesirable problems, such as entry of water, sand, dust or other foreign substances from outside, undesirable seepage of lubricant, such as grease, or displacement of the closing plate, which may cause dislocation of the ball stud.
As described above, the structure disclosed in Japanese Patent Public Disclosure No. 1998-100628 is incapable of improving the manufacturability of adjustable joint units, because it is necessary to form a tubular portion for crimping and securing the closing plate during the pressing process of the socket portion.
As each structure disclosed in Japanese Patent Publication No. 1977-29374 or Japanese Patent Public Disclosure No. 1993-76961 requires the vicinity of the rim of the mounting opening portion to be thin enough to permit its shape to be changed by crimping so as to be inclined inward, they are not only unable to improve the manufacturability of adjustable joint units but also present a problem in that the closing plate may not be attached with sufficient reliability.
In order to solve the above problem, an object of the present invention is to provide an adjustable joint unit which offers stable characteristics and improved manufacturability. Another object of the invention is to provide and a method of producing such an adjustable joint unit.
An adjustable joint unit according to the invention includes a ball stud having a stud portion that is provided at one end thereof with a ball head portion, a bearing seat which serves to contain said ball head portion in such a manner as to permit the ball head portion to slide therein and has an insertion hole through which said stud portion is adapted to be inserted, a generally plate-shaped arm having a generally cylindrical socket portion which serves to contain said bearing seat and is formed by a pressing process so as to have an axis extending in the same direction as the thickness of the arm and be open at both ends, with an aperture portion that permits said stud portion to be inserted therethrough being formed at the protruding end, i.e. the end facing the direction in which the socket portion protrudes, and a mounting opening portion at the base end of the socket portion, and a closing member which is adapted to be attached in such a manner as to close off the mounting opening portion at the base end of the socket portion and apply a given preliminary load to the ball head portion of the ball stud, wherein said socket portion of the arm has a crimped portion provided along the inner rim of said mounting opening portion and adapted to receive and hold the outer rim of said closing member, said crimped portion formed by crimping into a flange-like shape that extends inward and formed in steps having different thicknesses, with the inner step thinner than the outer step. As the inner rim of the mounting opening portion of the socket portion, which has been formed by pressing a generally plate-shaped arm, is crimped to form a crimped portion adapted to receive and hold the outer rim of said closing member and having a flange-like shape that extends inward and formed in steps having different thicknesses, with the inner step thinner than the outer step, the structure according to the invention increases the area of the surface where the closing member is received and held, and ensures the reliable contact and fixation of the closing member, thereby offering stable characteristics. Furthermore, the increased surface where the closing member is received and held improves the sealing ability of the adjustable joint unit and prevents entry of water, sand, dust or other foreign substances, undesirable seepage of lubricant, or other similar problems.
According to another feature of the invention, the crimped portion of an adjustable joint unit has a first step portion, which is formed along the inner rim of the mounting opening portion of the socket portion by crimping so as to extend inward in a flange-like shape, and a second step portion which is formed along the edge of the first step portion by crimping so as to extend inward in flange-like shape. As the crimped portion is formed by crimping the inner rim of the mounting opening portion of the socket portion to form a first step portion, which extends inward in a flange-like shape, and then crimping the edge of the first step portion so as to form a second step portion extending inward in a flange-like shape, the invention facilitates formation of a crimped portion which ensures the reliable contact and fixation of the closing member with an increased area of the surface in contact with the closing member, and has stable characteristics and improved sealing ability.
The crimped portion of an adjustable joint unit according to yet another feature of the invention is formed by a crimping process, which is conducted by rolling rotatable rollers along the inner rim of the mounting opening portion of the socket portion. As the crimped portion is formed by rolling the rollers along the inner rim of the mounting opening portion, the crimped portion can be formed easily and reliably.
A method of producing an adjustable joint unit according to the invention comprises the steps such that an arm is formed by pressing a generally plate-shaped arm base member so as to form a generally cylindrical socket portion having an axis extending in the same direction as the thickness of the arm and open at both ends, with an aperture portion at the protruding end and a mounting opening portion at the base end of the socket portion; a ball head portion of a ball stud is inserted from said mounting opening portion into the socket portion of the arm and contained therein, with a bearing seat between the ball head portion and the socket portion; a closing member is fitted in and thereby closes off said mounting opening portion of the socket portion; and that a crimped portion adapted to receive and hold the outer rim of said closing member is formed by crimping the inner rim of said mounting opening portion so as to extend inward in a flange-like shape that consists of steps having different thicknesses, with the inner step thinner than the outer step. As the inner rim of the mounting opening portion of the socket portion, which has been formed by pressing an arm base member, is crimped to form a crimped portion adapted to receive and hold the outer rim of said closing member and having a flange-like shape that extends inward and consists of different steps so that the crimped portion is thinner at its inner edge than is at its base end, the structure described according to the invention increases the area of the surface where the closing member is received and held, and ensures the reliable contact and fixation of the closing member, thereby offering stable characteristics. Furthermore, the increased surface where the closing member is received and held improves the sealing ability of the adjustable joint unit and prevents entry of water, sand, dust or other foreign substances, undesirable seepage of lubricant, or other similar problems.
A method of producing an adjustable joint unit according to another feature of the invention calls for forming a crimping portion so as to have steps having different thicknesses, with the inner step thinner than the outer step, by forming a first step portion, which extends inward like a flange, along the inner rim of the mounting opening portion of the socket portion, and then crimping the edge of the first step portion so as to form a second step portion extending inward like a flange. As the crimped portion is formed by crimping the inner rim of the mounting opening portion to form a first step portion, which extends inward in a flange-like shape, and then crimping the edge of the first step portion so as to form a second step portion extending inward in a flange-like shape, the invention facilitates formation of a crimped portion which ensures the reliable contact and fixation of the closing member with an increased area of the surface in contact with the closing member, and has stable characteristics and improved sealing ability.
A method of producing an adjustable joint unit according to yet another feature of the invention calls for forming a crimping portion by a crimping process, which is conducted by rolling rotatable rollers along the inner rim of the mounting opening portion of the socket portion. As the crimped portion is formed by rolling the rollers along the inner rim of the mounting opening portion, the crimped portion can be formed easily and reliably.